The date is in Thai numerals at the bottom of the reverse, below the seated figure: "109". This is in the old "Bangkok Era" calendar, where Year 1 is reckoned as the founding of Bangkok in 1782. Therefore, add 1781 to this year to get the AD equivalent: 1890.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis