Year before last, they (immigration office Chong Chom) saw that my balance had dipped to 720,000 at one point 2 months after renewal, and threatened to fine me. I think we resolved it by buying snacks and drinks for the whole office

At least they will negotiate. I had a funny 'border' experience in Indonesia some years ago. Flew in to Manado, North Sulawesi on the way to Gangga Island Resort with my wife. The official said that I did not have a full page free in my passport for their admittance stamp, and would have to go back to Singapore. But no flights left that afternoon. I suggested we discuss it, and so he took me into a back room (no witnesses) and I asked him if there wasn't a solution possible. He said $600 USD would solve the problem. Ah, a negotiation. I settled for $300 USD. The resort was waiting to pick us up, and the manager was pissed. He said that the head of immigration in Manado was in on it, and they had been targeting wealthy foreigners to shake down. The government in Jakarta wouldn't do anything about it.