As a former UK Driving Instructor (24 years part-time) having passed numerous advanced driving tests, several at high level + having driven a variety of vehicles in 14 countries: The OP turned across the path of an oncoming vehicle and collided with it. Before the days of magnetic boards with model vehicles I have drawn on paper this exact scenario as a learning point many times.
In many countries, the UK & Thailand included, it is to be expected that 2 wheelers will filter up the nearside of stationary traffic, legally or otherwise. As drivers we have to constantly make allowances for the mistakes of other road users. In Thailand it is the norm for m/cycle riders to do this & the OP should have been well aware of that.