Thailand

… The National Assembly, the Council of Ministers, Courts, Independent Organs and State agencies shall perform duties in accordance with the Constitution, laws and the rule of law for the common good of the nation and the happiness of the public at large. (Sec. 3)

The King appoints the Prime Minister and not more than thirty five other Ministers to constitute the Council of Ministers having the duties to carry out the administration of the State affairs in accordance with the principle of collective responsibility.
The Prime Minister must be appointed from a person who is approved by the House of Representatives under section 159. ... (Sec 158)

The House of Representatives shall complete its consideration for approval of the person suitable to be appointed as Prime Minister from a person who has the qualifications and is not under any of the prohibitions under section 160, and is a person listed by a political party under section 88, only with respect to the list of names of political parties whose members have been elected as Members of the House of Representatives constituting not less than five per cent of the total number of existing Members of the House of Representatives. ... (Sec. 159)

A Minister must:
1. be of Thai nationality by birth;
2. be not less than thirty-five years of age;
3. have graduated with not lower than a Bachelor’s degree or its equivalent;
4. be of evident integrity;
5. not have behaviour which is a serious violation of or failure to comply with ethical standards;
6. not be under any of the prohibitions under section 98;
7. not be a person sentenced by a judgment to imprisonment, irrespective of the finality of the case or a suspension of the punishment, except for an offence committed through negligence, a petty offence or a defamation offence;
8. not be a person whose office has been vacated on the grounds of committing any prohibited act under section 186 or section 187, for a period of less than two years up to the date of appointment. (Sec. 160)