It's settled, I shall wait until I'm in PNH to book the flight. BTW, apparently you cannot book that flight online through Bangkok Air. They said because it's operated by Siem Reap Airlines, you must call or email to book the flights. Directly from their email response to me:

*Routing :*

- Phnom Penh to Siem Reap and Siem Reap to Phnom Penh

================================================== ====================

*Flight time :*

_Phnom Penh to Siem Reap_

FT 990 : PNH - REP : 0645 am - 0730 am

FT 992 : PNH - REP : 0930 am - 1030 am

FT 996 : PNH - REP : 0550 pm - 0635 pm

_Siem Reap to Phnom Penh_

* *FT 991 : REP - PNH : 0810 am - 0900 am

FT 995 : REP - PNH : 0430 pm - 0520 pm

FT 997 : REP - PNH : 0705 pm - 0755 pm

================================================== ====================

*Ticket fare :*

_For one way : USD 60_

+ insurance and fuel surcharge (USD 9.5) + airport tax at Phnom Penh
(USD 6) + Value add taxes

for Domestic flight in Cambodia (USD 6 for one sector)

_For round trip : USD 120_

+ insurance and fuel surcharge (USD 19) + airport tax at Phnom Penh (USD
6) + airport tax at Siem

Reap (USD 6) + Value add taxes for Domestic flight in Cambodia (USD 12
for two sectors)

================================================== ====================

*How to make the reservation :*

- Please inform the itinerary as below if you would like to make the
reservation directly with us
via email or you can contact at Phnom Penh Town office for purchasing
the ticket.

1 . The passenger full name/surname/Title name/ nationality

- Title name is very important for making the reservation , please do
not forget yo inform us.

2. Contact number of homephone/businessphone/fax number with Area Code

3. The needed departure and destination city.

4. The departure time you need ( approximately ).

5. Inbound/Outbound connecting flight information including the
departure and arrival time.

6. Age and date of birth for child 2- 11 years or infant under 2 years.

================================================== ====================

*Paying and Issuing the ticket*

- You can pay and pick up the ticket at Phnom Penh Office 1-2 days
before on travelling date.

_Phnom Penh Town Office _

Address : No.61 A St. , 214 Sangkat Beong Rang , Khan Don Penh , Cambodia

Telephone number : + 855 (23) 722 545-47

Fax number : + 85 (23) 725 502

E-mail : [email protected]
<mailto:[email protected]>

Working hours : 0800 am - 0400 pm (everyday except Sunday)