Upvote:7
As of 2019, the official waiting time tariff for taxis in Bangkok is 3 baht per minute. But cabbies can be nervous about passengers leaving before payment and not coming back, so it's safer for them to get paid for the fare so first, and then restart the meter on return. Restarting the meter also gives you another 2 km for "free" (included in base price), so for a stop of 5-10 min the price difference will be minimal.
Source: https://workpointnews.com/2019/08/07/taxi/ (in Thai)