My take (vast!) on the hagglin' game goes generally like this. Firstly I only haggle at the beach and lots of Thai markets.
Start at 20% off. They will take a pouting offence and laugh. Then I offer 10-15% off and some seconds later I walk off having haggled an OK 12%. Big deal.
If I'm in the mood I'll haggle, if not I pay full price plus a small tip.

Once I tried haggling at Bangkok Paragon (just for fun) and was leered at in disdain. Covered my tracks by "just joking ha ha ha".