The reference you have is from an LDS Family History Centre or website. It would be a microfilm of the existing register, but only available through one of the Family History Centres. Seeing where you live that is going to be a problem for you as there are none in Vietnam. The closest is in Thailand or Cambodia - you can find details on their site:
family search.org
Alternatively you can contact the Bristol Record Office direct and see if they can send an electronic image:
bristolmuseums.org.uk
It might be worth asking on Rootschat (Gloucestershire lookup requests) to see if anyone visits the Bristol RO regularly who might be able to copy and send it for you. I do go to Bristol from time to time, but I don't know when that might be next.
Do you have access to Ancestry? If so the record of the trial of Thomas Larkham a blacksmith of St Augustines parish (which is where your Thomas lived in later life) might be of interest. It gives a good physical description of him. This could be your chap.He was acquitted by the way.
Concerning Elias, who "Capetown" found, I recall, this is a promising lead. He was born in Banwell, Somerset in 1762 and apprenticed there to a carpenter in 1787. In 1790 he married Hannah Collings in Bristol and they had the following children:
William 1791
Elizabeth 1793
John 1795
Eleazar 1797
Edith 1800
He was living with his daughter in Bitton in 1841, but seems to have died later that year and was buried at St Mary Redcliffe in Bristol, where Hannah had been buried in 1833. Their eldest son, William was baptised at Temple church, but all the others were baptised at St Johns, Bedminster. Now Bedminster, although part of Bristol since the 1890s, was in Somerset then, so it may be that Thomas was one of theirs too, hence born in Somerset. Sadly I still can't find any baptism for him, so it's just a guess.
As for looking at parish registers, Somerset's are all on Ancestry now, but Bristol parishes (including Bedminster and other places nearby but in Somerset historically at the Bristol RO and not on the internet (yet),
Steve