Filling the Pre-school (Thai) to Grade 1 (Int'l) Gap

My daughter, age 5 (6 in April), has been attending a good English Program pre-school that runs on the Thai school calendar. She will move to an international school for Grade 1. The pre-school ends in March and the international school new year starts in August. What do people do to fill this 3+ month (May to July) gap? The international schools suggest that my daughter start in late April in the 3rd term of Grade 1 and move with her class to Grade 2 in August. Her basic skills (Thai and English) seem to be very good, but I would prefer her to have a full year in Grade 1. Another option is to put her in a private Thai school with an English Program in May and then move her to the international school in August. Lastly, we are considering putting her in the international school in April and asking the school if she can repeat Grade 1 starting in August. Having her "sit out" the 3 month gap is not an option that we would consider. Have others faced this situation? What have you done, and has it worked well for your child (and you)? Thanks,