I am a British passport holder currently living in Vietnam.

As I'm planing to travel for leisure to Thailand several times through the year,I would like to ask which way is the best/hassle free to enter Thailand occasionally. 

 

Thank you.

The best way would be to get a METV (multi entry Visa) from the UK...but failing the ability to do that, a tourist visa from the Thai embassy in Hanoi would give you 60 days extendable by 30 days in Thailand. If you chose to only stay a portion of that 60 days + 30, you could purchase a re-entry permit in Thailand to facilitate leaving and re-entering during the valid period of the visa.

As you're asking about entry into Thailand, I'll move this post to the appropriate forum.

You would get a 30 day visa exempt entry when you arrive.

Or as said you could get a single entry tourist visa at the embassy in Hanoi or  at the consulate in Ho Chi Minh city.

If you have a residence visa for VN and have a job you can get a multi entry tourist visa.