I was in Phuket in April this year, and yes there are plenty of Russians, but that's generally always been the case for Thailand.
Some shops/restaurants will have signs written in English as well as Russian, but they didn't cause us any bother.
There's plenty of other nationalities kicking about too, so it's not exclusively Russian or anything like that.
Coconut island just off Phuket has caught our eye, like I said no nothing about it!! cheers for your help & advice mate ;)
Khao Lak north of Phuket is beautiful and a little quieter.
Bangkok is always fun and worth a visit.
Samui, Krabi, Phi Phi all worth considering too.
They have Songkran festival around the middle of April, so if you don't like getting wet then avoid that completely.
Would also avoid Easter too for the better prices on flights etc