Passing indicators are used primarily in a situation where passing is imminent, such as a slower moving truck or bus that sees the car behind them is attempting to pass and may not be able to see around them. Most drivers use this method on open 2 lane highways, not in cities where numerous turns exist. And a motorcycle would never use this method, as they would simply move to the edge of the lane so faster moving vehicles can safely get around them (90% of scooters in Thailand drive on the edge of bigger highways all the time).
So using the turn signals on your motorcycle would tell the other drivers that you are turning. They would not view it as a passing suggestion and you should not use it as a passing suggestion to them.
How can you tell if the vehicle ahead that is signaling you is turning or suggesting you pass? If they are slowing down, then they are planning to turn. If they are maintaining speed AND you have been following them peeking around to watch oncoming traffic for a bit, then they are suggesting it is OK to pass.
You make your turn same as you would at home, use your turn signal, command the lane, move to the right of the lane as you approach your turn. If you are on a scooter without power on a busy highway, most Thais will pull onto the shoulder and wait for clearing in both directions before crossing, so as not to be sitting in the middle of fast moving vehicles on the highway waiting.
Some other turn signals anomalies you might encounter …
If a faster moving vehicle unexpectedly has to slow (say a truck moves over to pass an even slower truck in front of them) the faster moving vehicle driver will flick back and forth between his turn signals, turning the left on, then the right, then the left, etc., for just a few seconds. This is the Thai version of warning flashers.
A truck on a divided four lane highway in the right lane going slow with his right turn signal on and there is no obvious turn coming up, usually means he will be using the next U-Turn, which maybe a long ways up the road (but the driver knows it is coming up).