According to this translation, from a law office and not the government, the Constitution of the Kingdom of Thailand B.E. 2550 (2007) the only part relevant seems to be this:
National Security Policy
Section 77.
The State shall protect and uphold the institution of kingship and the independence and integrity of its jurisdictions and shall arrange for the maintenance of necessary and adequate armed forces and ordnances as well as up-to-date technology for the protection and upholding of its independence, sovereignty, security of State, institution of kingship, national interests and the democratic regime of government with the King as Head of State, and for national development.
http://www.asianlii.org/th/legis/const/2007/1.html#C01
If your interests are related to the 2006 Coup, Section 309 refers:
Any act that its legality and constitutionality has been recognised by the Constitution of the Kingdom of Thailand (Interim), B.E. 2549, including all acts related therewith committed whether before or after the date of promulgation of this Constitution shall be deemed constitutionally under this Constitution.
B.E. 2549 Section 37 states:
All acts done by the Chairman of the Council for Democratic Reform which related to the seizure and control of the State administrative power on 19th September B.E. 2549 as well as any act done by persons involved in such seizure or of persons being assigned by the Chairman of the Council for Democratic Reform or of persons being commanded by the Chairman of the Council for Democratic Reform which done for such above act. All these acts, whether done for the enforcement in legislative, executive or judicial force as well as the punishment and other acts on administration of the State affairs whether done as principals, supporters, instigators or persons being commanded to do so and whether done on such date or prior to such date or after such date which if such acts may be unlawful, the actors shall be absolutely exempted from any wrongdoing, responsibility and liabilities.
http://www.asianlii.org/th/legis/const/2006/1.html