Just back from 10 days Thailand, both hotels offered good upgrade:

Hilton Arcadia Phuket: booked standard twin, upgraded to Junior Suite twin in Lotus Wing. Enquired after 1st night about Hilton Suite and was offered for remainder of stay. Upon viewing decided not to move: suite was little larger etc but a very long way from Panorama Lounge.

Hilton Millenium Bangkok: booked Exec King Room and upgraded to Exec King Suite. Lovely room with Desk/Sitting Room area and separate bed/bathroom. If any criticism the bathroom is not in proportion to the rest (i.e. small).