Which immigration office in Bangkok is best for extending a tourist visa by 30 days?

First off lets make SURE that you're really on a 'tourist visa'. :O So before you came here you BOUGHT a tourist visa from a thai consulate in your country and when you arrived you were stamped in for 60 days right?

The reason I ask is IF you entered on a real tourist visa you go to Chaengwattana to get your 30 day extension BUT if you entered on a 45 day visa exempt entry stamp you go to the alternation office out at Muang Thong Thani.

In Bangkok you can apply for an extension when you have 45 days or less left on your current stamp. SO if you've been here 2 weeks you can go apply for the 30 day regular extension now and they'll add it to your current expiration date

> is the Best to extend my tourist visa for 30 days.

There is no "best" immigration office to use. The only immigration office you can use is Changwattana.

Immigration is closed tomorrow, and will reopen on Friday.

>I‘ve only been here for 2 weeks

If my memory serves me right, you can only extend it when you have 30 days or less remaining on your current stamp.