I would say it is highly unlikely that international schools will make up for lost time during the Summer break. I work at an international school in Bangkok and I am not aware of any schools that will do this. I can only see this happening with smaller schools that have had parents complain about paying full fees for online learning.
Most of the feedback I have seen online from parents with students at decent schools has be very positive and supportive of the distance learning that their children have received. Additionally, a lot of teachers are planning to move to new schools over the summer and will not be available to continue working at their current schools. I, for example, have accepted a job in Vietnam and hope to move there in June/July, covid permitting.
I will add this may be the chance for someone with a little teaching experience and a degree in a specific subject to make the jump into an international school as a late hire because someone from abroad can't make it to Thailand in July.