bắt cá hai tay (Vietnamese) = catch fish with two hands (two-timing) The same expression, means in Thai completely different. I happened to read it in one of Vanda's posts.

In the USA, "two-timing" is an old expression. We still understand it, but we usually say "cheat" or "cheat on." Good luck!

Yes, it is common in the UK. "Cheating on" and "two-timing" are equally as common as each other in British English.

"two-timing someone" - be unfaithful / unloyal.

I agree with Matt that they are as common as each other here in Britain although to my mind they have slightly different meanings. "Two-timing" sounds more deliberate to me, and implies something longer-term. "Cheating on" can mean that, but also can be something that only takes five minutes. So you could say "Did you cheat on me last night with Keeley? Jackie says she saw you snogging her" but you would never say "Were you two-timing me last night?"