Nervous Exchange Rate -- How To Transfer?

I'll need to transfer a large amount (THB 1.4m) to Thailand soon and am somewhat nervous about jittery exchange rates (CHF/THB) and not having any sort of control over it.

I do "bite sized" transfers regularly [family support] from a Swiss bank in CHF; that gets converted to THB as it hits the receiving bank 3-4 days later, at whatever exchange rate someone there sees fit. Normally, I simply foam at the mouth when I happen to get a down day (like: I lose a few hundred THB compared with previous/next days exchange rate), but with a large amount like this, there's a LARGE difference between any two banking days' exchange rates (like: a new 125cc motorbike...).

Rate fluctuations are currently quite massive, within a single day, and worse over the course of a few days. My Swiss bank tells me that they don't do "controlled" exchange rate transfers with amount under CHF 100k to THB, because THB isn't a "standard"/"convention" currency. ###### gnomes but what can you do... Problem is also that I currently live in Switzerland and can't quickly open a foreign-currency account in BKK. I'll also need a "tor tor sam" (proof that the funds came from abroad), because the stash of cash is destined for a condo...

Anyone with a suggestion on how to make the jittery bit a little more controllable? Thanks!