Ok here's an update. Check in for flight back at Vietnam airline desk was asked if had an onward flight from LOS , I just said yes she was happy with that. Good job she did not want to sight it as I only took one copy with me and the embassy now had that. So I would advise having 2 copies of onward flight, one for embassy and a spare. I was also asked if I worked in Bangkok ( trick question as she must have seen my visa was tourist ). Now being 62 I rather offendedly said: " no I'm retired ". Arrival at Swampy, all immigration queried was my address that I'd put on the arrival card ( private addy not hotel ) they wanted to know the sub district, did not really know want he wanted so I just told him near Ban Phe. Happy with that I was waved through. No mention of 20,000 Baht ( that I'd been travelling around with for the past week) or onward flight.