This is SIAM LAKJOONG 2 - IMO 7505712

See http://www.shipspotting.com/gallery/photo_search.php?query=7505712

The addition of the Off.No.301041565 to the bridge name board removes any doubt

THANKS YOU VERY MUCH FOR YOURS ALLS INFORMATION (steph)

She is a tug. I've photos of her at Koh Sichang, also with a floating crane, so she's probably owned by the same company. Her name may be SIAM KULAKHAN 2, but I'm afraid I can find no more information about her.

Looks like a former German tug. Definitely not a supply vessel as there is no clear deck space abaft the superstructure.
Brgds
Phil