Interesting. Yes you're right it does currently say 10. Perhaps it temporarily said 20 before. They don't offer a 30 option so it jumps from 20 to 40. So sometimes I'll do the 20 when paying online and if the service was exceptionally good like very long ride, rain, super quick etc. I'll give them an extra 20 on arrival. I could give an extra 10 but coins feel unseemly. When I do thst its embarrassing how greatful.they are Not judging you but I do think 10 total is really not good enough.
On Grab you can choose a custom amount so I pay 25 or 30 which is paid after delivery unlike Panda.
Occasionally the service is crap like they make two other deliveries before and the food is cold in which case I don't tip at all.
I do wonder if the drivers have access to customer tipping records. If they do I would expect them to avoid non tippers.
While I'm against tipping American style percentage of check in Thailand I still do very much appreciate how affordable delivery services are here in comparison and also that doing bike deliveries is hazardous and underpaid work. What's a luxury service there is much more widely accessible here.