HI,
How to I make complicated air reservations? Do you use a travel agent or book online?

SFO to Singapore
Singapore to Bangkok
Bangkok to Siem Reap
Siem Reap to Taipei
Taipei to SFO

Any ideas?
thanks,
KSC

Your itinerary is easily done online, several flights but quite straightforward. Here's how I'd approach it:

Book the long-haul flights, SFO to Singapore & Taipei to SFO on 1 ticket. Compare various airline fares or whatever criteria you prefer. Edited to add: When searching for the long-haul flights from & return to SFO, use "Multi-City" rather than one-way or round-trip.

Start here to compare: https://www.skyscanner.com/
Or here: https://matrix.itasoftware.com/search

The rest, the flights within Asia I'd book individually using low fare Asian airlines.
My favorite is Air Asia. https://www.airasia.com/en/gb

Of course you do. Travel agencies always do.

I would book your main international flights as and "open jaw" ticket SFO to Singapore out and Taipei to SFO back. I tend to use google flights to determine which airline fly those routes and then book direct with the airlines.

Most of your regional flights I would book with regional budget airlines. Air Asia are my preferred choice simply because they have the widest range of routes and their booking process/app are very user friendly but there are many others from which to choose.

You should be able to source direct flights with the exception of Siem Reap to Taipei which will almost certainly require a connection, most likely in Bangkok. An alternative would be to rearrange your itinerary to fly to Taipei from somewhere else or, after Siem Reap spend a couple of nights in Phnom Penh which is a great city to visit and from where there are direct flights to Taipei.

Booking on-line is feasible, but, with such a complicated itinerary, I would recommend a travel agency;;

I'm curious -- why? What are the advantages you think would accrue from using a travel agency?

In your case, a travel agency is better because booking flights is the "bread and butter", so they know what they are talking about. Moreover, Internet flight schedules are not always accurate, with flights not existing any longer or prices not reliable Finally, airlines do not always inform you of problems such ass a flight cancellation; agencies do

In my experience, none of the above.

I don’t know when you plan to go. As for the suggestion of putting in the long-haul flights first I put in dates in February and found a fantastic airfare on Cathy Pacific for this route, SFO-SIN and TPE-SFO for only 820 bucks.

Ask for the rest, I would suggest what others have said and use air Asia for those local routes.

When do you plan to go?

Agree with crellston. I do fine tune with ITA Matrix. No need for a TA for this.

This isn't all that complicated, as you are not on a super tight itinerary, are you? See if you can book all or most of the big destinations, e.g SFO-SIN-BKK-Taipei-SFO on one airline. Finish by filling in the gaps (BKK-Siem Reap-BKK or BKK- Siem Reap-Taipei on Air Asia or one of the other asian airlines.)

This in my opinion isn’t really a complicated reservation, you can book this flight on most all website using the “multi destination” or “multi city” booking option. If you mean how do you do it to find which dates are the cheapest, the best thing to do is to search for round trip flights for each destination, find the cheapest prices for one way flights for each destination from the destination you will be flying there from, and then piece it together like that before switching to a multi destination booking which most of the time will be alot cheaper than booking them as one day flights .

for example. Search for flights from SFO to Singapore one way and find the cheapest dates and then one way from Singapore to Bangkok and so on. And then go build the trip using the multi destination booking.
Dont be nervous, you have 24 hours to cancel any booking for a full refund if you make a mistake. Just triple check everything before and after booking to ensure it’s all good to go before that 24 hour window hits.