The current construction is to provide dual one metre gauge tracks and not so called 'high speed' This will reduce journey times by eliminating delays waitng on passing loops for trains passing from the opposite direction. The refurbished ex-Japan Railways locos and rolling stock will be used for passenger services. In due course, track will be upgraded to standard gauge (?) for 'high speed' trains and it is likely that the new HH station accommodates that plan. Given the economic downturn in far Cathay I should not expect more money from them and expansion will have to be funded by Thailand.
As an aside, Nong Gae station (barely a Halt) is nowhere near the stated waterpark.