Links:
http://www.tribalmusicasia.com/
A very good blog about the music of the "Golden Triangle" by  Victoria Vorreiter

https://www.thaisounds.com/ethnicmusic.htm
A page with many audio samples of music from various ethnic groups

https://goldentriangleinstruments.wordpress.com/
A very good blog about various instruments of the "Golden Triangle"

https://www.thenotedproject.org/
A project introducing the Karen musicians´on the Thai-Burmese border

https://culturalcrossroadsasia.org/
Homepage of the "Cultural Crossroads" Project, featuring videos, pictures and audio files of the ethnic groups in the golden traingle

http://archive.org/details/calauem_201405_I-E_clip_Music_of_Thailand
A movie of the UCLA Music of Thailand Ensemble from 1972

http://sonicsafarimusic.com/music/thaifolkmusic/
Audio exmaples of Thai Folk music by "Sonic Safari Music"

http://www.indigenius-recordings.com/
Recordings of the music of ethnic minorities in Thailand

SHOPS:
https://thegongshop.com/collections/thai-gongs?srsltid=AfmBOoosSObBg5_KwGW-A7zoYJRCpNOMq-c07O4lkQXGwp1u9LeRcMb3
The Gong shop offers sets and single bossed gongs from Thailand

http://musical-instruments.novica.com
The "Novica" store in Thailand, also selling musical instruments