In a pot, bring coconut milk, palm sugar, granulated sugar and salt to the boil. This liquid should taste sweet but not sickly sweet, followed by a little bit of saltiness to balance it out.
Once it has achieved the desired taste, add the banana pieces and bring back to the boil. Correct the seasoning again, because Thai bananas are more sour than Cavendish bananas. Allow the banana pieces to soften and to take on the flavor of the coconut milk (about 10 minutes). Turn off the heat.