Just sharing a tip based on my personal experience, for those looking to exchange money in Bangkok, Siam Exchange at Pathum Wan (near MBK & Siam Station) has one of the best rate I can find, better than those in MY as well. I found this place based on google reviews and can confirm the reviews are true.
But do remember to bring your passport, I forgot to bring mine but luckily I kept a photo of it in my phone which they accept but reminded me to bring the original passport next time.

Cool Thanks for sharing.

I travel to Kanchanaburi via train from Bangkok and came back using van. Both took roughly the same duration because of the frequent train stops.
Train offers a more scenic route but you have to be at the station early because there's only one train departing early morning, and there's no AC on train, so be sure to bring a portable fan.
Another advantage of train is you can travel all to way to the river kwai bridge.
I stayed at River Kwai View Hotel and booked a songthaew (open-air truck) to Erawan in the morning.

Suvarnabhumi airport should be better since that's where most full service airlines are based, I took the Airport Rail Link to and from airport, no issue and quite convenient if you stay near a station.