Unless explicitly exempted, majority foreign investment in all services sector activities is subject to approval under the Foreign Business Act (List 3, parag. 21). 
[In the OECD FDIRRI, it is assumed that all services sectors, which are not explicilty excluded from FBA purview nor are explicitly subjected to minority foreign equity holdings under sector-specific legislation, are subject to discriminatory screening under list 3, parag. 21 of the Foreign Business Act. The FBA does not follow a standard sector classification and electricity generation is not explicitly excluded from the list of sectors subject to approval. Since electricity generation is sometimes understood as a service sector, it is assumed to be subject to such approval requirement].
"Section 4
In this Act, “foreigner” means:
1. a natural person who is not of Thai nationality;
2. a juristic person not registered in Thailand;
3. a juristic person registered in Thailand, being of the following descriptions: 
a. being a juristic person at least one half of capital shares of which are held by persons under (1) or (2) or a juristic person in which investment has been placed by the persons under (1) or (2) in the amount at least equivalent to one half of the total capital thereof;
b. being a limited partnership or a registered ordinary partnership the managing partner or the manager of which is the person under (1);
4. a juristic person registered in Thailand at least one half of the capital shares of which are held by persons under (1), (2) or (3) or a juristic person in which investment has been placed by the persons under (1), (2) or (3) in the amount at least equivalent to one half of the total capital thereof; 
[...]
Section 8
Subject to section 6, section 7, section 10 and section 12:
1. no foreigner may operate such businesses stricto sensu not permissible to foreigners by special reason, as prescribed in List One;
2. no foreigner may operate such businesses related to national safety or security, businesses having impacts on arts, culture, traditions, customs and folklore handicrafts or businesses having impacts on natural resources or the environment, as prescribed in List Two, unless upon obtaining permission from the Minister with the
approval of the Council of Ministers;
3. no foreigner may operate such businesses in respect of which Thai nationals are not yet ready to compete with foreigners, as prescribed in List Three, unless upon obtaining permission from the Director-General with the approval of the Commission.
[...]
Annex [...] 
List three. Businesses in respect of which Thai nationals are not ready to compete with foreigners  [...] 
(21) Other service businesses, with the exception of service businesses as prescribed in the Ministerial Regulation"((Foreign Business Act, B.E. 2542 (1999))
------------------------------
"By virtue of the provisions of section 46 paragraph one of the Foreign Business Act, B.E. 2542 (1999) and List Three annexed to the Foreign Business Act, B.E. 2542 (1999), which is the law containing certain provisions in relation to the restriction of rights and liberties of persons, in respect of which section 29 in conjunction with section 33 and section 43 of the Constitution of the Kingdom of Thailand so permits by virtue of provisions of law, the Minister of Commerce issues this Ministerial Regulation, as follows. The following service businesses are the service businesses excluded from (21) of List Three annexed to the Foreign Business Act, B.E. 2542 (1999):
(1) Securities business and other businesses under the law on securities and securities exchange:
 (a) securities trading; (b) serving as an investment consultant; (c) securities underwriting; (d) borrowing and lending securities; (e) mutual fund management; (f) private fund management; (g) venture capital management; (h) granting loans for securities business; (i) serving as a financial consultant; (j) serving as a securities registrar;
 (k) trusteeship of assets of securities companies’ or derivatives traders’ customers; (l) serving as a private fund custodian; (m) serving as a mutual fund supervisor; and
 (n) serving as a debentureholders’ representative;
(2) Serivatives business under the law on derivatives:
 (a) serving as a derivatives dealer; (b) serving as a derivatives advisor; and (c) serving as a derivatives fund manager; and
(3) Serving as a trustee under the law on trust for transactions in capital market.
(4) financial institution business, businesses incidental to or necessary for the operation of a financial institution business and the businesses of companies in the financial group of a financial institution pursuant to the law on financial institutions [amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]:
 (a) commercial banking business;  (b) bank representative office service business;  (c) Shariah financial service; (d) financial institution agent; (e) cash deposit services under terms of withdrawal on demand by a customer and custodian services; (f) private sector repurchase; (g) agent to receive applications and collect insurance premiums or service fees for export insurance and credit insurance for customers; (h) services relating to financial businesses offered to financial institutions, companies within the financial group, the Bank of Thailand and government agencies; (i) leasing of immovable property; (j) purchase or assignment of loan debts; (k) financing service; (l) documentation relating to customer’s businesses; (m) debt collection or application receiving agent;  (n) hire purchase and leasing.
(5) life insurance business under the law on life insurance; [as amended by Ministerial Regulation Prescribing Service Businesses which Do Not Require a Foreign Business License (No. 2) B.E. 2559 (2016)]
(6) insurance business under the law on insurance.”[as amended by Ministerial Regulation Prescribing Service Businesses which Do Not Require a Foreign Business License (No. 2) B.E. 2559 (2016)]
(7) asset management business under the law on asset management company; [amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]
(8) representative office of foreign juristic person in international trade service pursuant to the Rules of the Prime Minister’s Office on Establishment of Visa and Work Permit Service Center B.E. 2540 (1997);[amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]
(9) regional office of foreign juristic person in international trade service pursuant to the Rules of the Prime Minister’s Office on Establishment of Visa and Work Permit Service Center B.E. 2540 (1997);[amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]
(10) service business to which a government agency under the law on budgetary procedures is a party;[amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]
(11) service business to which a state enterprise under the law on budgetary procedures is a party[amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)]. "(MINISTERIAL REGULATION PRESCRIBING SERVICE BUSINESSES NOT SUBJECT TO APPLICATION FOR FOREIGN BUSINESS PERMISSION, B.E. 2556 (2013); amended by Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017), Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 2) B.E. 2559 (2016))
Foreign Business Act, B.E. 2542 (1999)
MINISTERIAL REGULATION PRESCRIBING SERVICE BUSINESSES NOT SUBJECT TO APPLICATION FOR FOREIGN BUSINESS PERMISSION, B.E. 2556 (2013)
Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 2) B.E. 2559 (2016)
Ministerial Regulation Prescribing Service Businesses Which Do Not Require a Foreign Business License (No. 3) B.E. 2560 (2017)
[<a href=" https://investmentpolicy.unctad.org/investment-laws/laws/40/thailand-foreign-business-act">Act</a>],[<a href="http://www.dbd.go.th/dbdweb_en/ewt_dl_link.php?nid=4059">Reg</a>],[<a href="http://www.dbd.go.th/dbdweb_en/ewt_dl_link.php?nid=4217">Reg</a>],[<a href="http://www.dbd.go.th/dbdweb_en/ewt_dl_link.php?nid=4219">Reg</a>]