Why does my chain come off the Chainring?

[Ajax Bay]

Looking at how the chain is falling off, I think the chain ring needs to go slightly inboard, all these chain guides do is mask the real problem, you shouldn’t need one if it’s set up properly.

The chain is falling off 'outwards' so the chain is arriving at the chainring and 'preferring' to drop to the right. If the OP does what you advise and move "the chain ring . . . slightly inboard" then the angle will increase, and with it the risk of dropping the chain. So I think the opposite, and said so upthread.

That's exactly why I have come to cc 😀

What, so you can consume conflicting advice?
I said: "the single chain ring is well further in than the designed chainline. I'm guessing this had a triple on before."
Measure the chainline of your fourth sprocket (Sheldon describes how) and get your new 1x chainset on that chainline. The e-bay link to their new chainset the OP shared gives no indication of the required spindle length: a sign to me (apart from low price) that its quality is 'not assured'.
Compare with: https://www.spacycles.co.uk/m8b17s109p4546/SPA-CYCLES-TD2-Spa-Narrow-Wide-Single-Chainset (specifies a 110mm spindle btw)

 

[Gunk]

The chain is falling off 'outwards' so the chain is arriving at the chainring and 'preferring' to drop to the right. If the OP does what you advise and move "the chain ring . . . slightly inboard" then the angle will increase, and with it the risk of dropping the chain. So I think the opposite, and said so upthread.

first glance of the photo, it looked as if it was falling off towards the BB, I stand corrected

 

[sleuthey]

Thanks for all the suggestions. When I fit the NW chainring, hopefully by this time next week, I will choose a spindle that ensures it's a few more mm outboard of the frame.

 

[sleuthey]

@T4tomo
@Ajax Bay
@ColinJ
@GuyBoden
@Gunk
@tripletail52

UPDATE:
The 36T NW chainring arrived a few days after my post which I fitted with and old Truvative Crank and a 103mm BB I already had. It's been ridden a couple of times a week for the past 6 weeks with no chain issues at all. Drivetrain is sublime.