From Thailand: the nearest major town is Kanchanaburi. There are frequent bus services from Kanchanaburi to Sangkhlaburi 4-5 hours, from where you can continue by pickup truck 30-40 min, departures hourly.
From Myanmar: the nearest town is Payathonzu, however foreigners can only get there using the border crossing from Thailand. The border crossing at Three Pagodas Pass is in a state of flux, but has been reopened as of December 9, 2010. as of January 19th 2012 it was open to Thai citizens but NOT open to foreigners.
