Had the same problem 2 weeks ago with the BKK-SIN
Before taxes 1435thb
After taxes (on the 1st page) 2135thb
and it says Total + Taxes + Surcharge , so i thought that was cheap, infact cheaper than LCCs
Then once I proceed to the next page, the price changed to 4085thb
Last week they seems to have fixed the problem, it's 5955thb now .
But this isn't the 1st time I seen this, previously I've seen a RM 9 ticket KUL-PEN (again it says total + taxes + surcharge) but once i click on the next page it changes to RM129.