Going from Tamil to Thai (เธ เธฒเธฉเธฒเนเธเธข) has a composite linguistic distance of 88% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Tamil โ Thai
Dravidian โ Tai-Kadai
The 5 languages with the lowest linguistic distance from Tamil:
A quick 3-question check between Tamil and Thai. No signup.