The Atlanta is situated at number 78, Soi 2 Sukhumvit Road.  The telephone numbers are 02-252 6069 and 02-252 1650.  The 02 is the prefix for Bangkok landlines and must be used when calling from any telephone in Thailand.

'Soi' means lane; so 'Soi 2' means lane number 2; Sukhumvit Road is a major thoroughfare. 'Soi 2 Sukhumvit Road' thus refers to lane number 2, off Sukhumvit Road.  The Atlanta is a five storey building on the right hand side at the end of this lane and adjacent to the Calvary Baptist Church.  The lane is 600 metres / yards long.  [Clarifying confusions:  Soi 2 Sukhumvit Road also has a name.  The name is usually spelt Phasuk.  It is sometimes spelt Pha-Suk.  It is pronounced Paa-sook (not Fa-suck).  This name has not been in current use since the 1950s when Bangkok was a much smaller city, and few today know it.  Everybody, including taxi drivers, uses the lane number.  On the google map below, Soi 2 Sukhumvit Road is called 'Sukhumvit 2 Alley'.  Nobody calls it thus, not even the ex-pats.  No taxi driver would understand 'Sukhumvit 2 Alley' even if he speaks English.  If you point the cursor at the red marker for The Atlanta Hotel and click it, the address will pop up on the top left corner of the map, 'Soi Sukhumvit 2 (Pha Suk)'.   It should read, 'Soi 2 (Paa-sook) Sukhumvit Road'.  Place names and their abecedarian spellings are not and have never been standardised in Thailand; and it may be too much to expect global cartographers to get it right everywhere!]   

A useful landmark is the J.W. Marriott Hotel at the corner of Soi 2 Sukhumvit Road.  If you find this J.W. Marriott, you are 600 meters / yards from The Atlanta.  [Avoiding confusions:  There are two Marriott Hotels on Sukhumvit Road - one at the corner of Soi 2 (which is your landmark), the other at the corner of Soi 57 (which is not your landmark).  There are also many Marriott Executive Appartments in the city.]
The entrance to The Atlanta Hotel is quite difficult to find until you are "on top of it".  However, look carefully and you will see the main entrance between two signs.  One reads: "This is the place you are looking for, if you know it. If you don't, you'll never find it".  This is absolutely true: nobody comes to The Atlanta by chance.  The other more famously reads: "Sex tourists not welcome".

Arranging transport by taxi to The Atlanta from either of Bangkok's two airports can be done in English, so it is not necessary that you have the address in Thai.
Arranging transport by taxi to The Atlanta from other entry points to the city, like the various bus terminals and railway station, CANNOT easily be done in English.  You are advised to print out or copy the address in Thai and the telephone numbers to show to the driver or passers-by.