Going from Tatar to Khmer (ភាសាខ្មែរ) has a composite linguistic distance of 93% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Cyrillic → Khmer
Turkic ↔ Austroasiatic
The 5 languages with the lowest linguistic distance from Tatar:
A quick 3-question check between Tatar and Khmer. No signup.