Thai Sign Language (TSL; Thai: ภาษามือไทย), or Modern Standard Thai Sign Language (MSTSL), is the national sign language of Thailand's deaf community and is used in most parts of the country by the 20 percent of the estimated 56,000 pre-linguistically deaf people who go to school.

[3] These original sign languages probably developed in market towns and urban areas where deaf people had opportunities to meet.

They are now considered moribund languages, remembered by older signers but no longer used for daily conversation.

[5] These older varieties may be related to the sign languages of Vietnam and Laos.

[6] Thai Sign Language was acknowledged as "the national language of deaf people in Thailand" in August 1999, in a resolution signed by the Minister of Education on behalf of the Royal Thai Government.