The trip inclusive of air fare, room and transport cost about S$900 for the 8 days.
The traffic jams in Bangkok is serious and it would be beneficial to stay in hotels in town instead of the outskirts. Thai food and coffee are delicious and cheap, Electronic goods are not cheaper than Singapore though. We booked an 11 seater van for 2000 thai bhatt per day.
From Bangkok to Hua Hin is about 250 km.