Foreign investment in domestic land transportation services is limited to 75% of equity ownership and at least two-fifths of directors need to be Thai citizens.
"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.
[...]
Section 15
A foreigner which is a juristic person may operate any business specified in List Two only where not less than forty percent of its shares are held by Thai nationals or juristic persons which are not foreigners under this Act, save that, where there is a reasonable cause, the Minister with the approval of the Council of Ministers may reduce the proportion in this matter, provided that the required shareholding must not be less than twenty five percent and that not less than two-fifths of the total number of its directors must be Thai nationals.
[...]
Annex [...]
List two. Businesses related to national safety or security or having impacts on arts, culture, traditions, customs and folklore handicrafts or natural resources and the environment [...] Chapter I. Businesses related to National Safety or Security [...]
2. Domestic transportation by land, water or air, including domestic aviation [...] "((Foreign Business Act, B.E. 2542 (1999))
Foreign Business Act, B.E. 2542 (1999).
[<a href="https://investmentpolicy.unctad.org/investment-laws/laws/40/thailand-foreign-business-act">Act</a>]