I do RTWs out of SGN fairly regularly and have gotten the following prices. When I do my ST RTWs, I get my tickets from Air France's office whose prices are pretty much harmonized with *A's RTW rates.

COACH
RTW Special (26,000 miles) - $2,399
RTWSKY1 (29,000 miles) - $2,889
RTWSKY2 (34,000 miles) - $3,319
RTWSKY3 (39,000 miles) - $3,899

BUSINESS
RTWSKY1 (29,000 miles) - $5,679
RTWSKY2 (34,000 miles) - $6,559
RTWSKY3 (39,000 miles) - $7,699

FIRST
RTWSKY1 (29,000 miles) - $7,859
RTWSKY2 (34,000 miles) - $9,079
RTWSKY3 (39,000 miles) - $10,669

So if you ever decide to do an RTW out of SGN, these are fairly up-to-date prices.