Electrical – Install new wall outlet few feet to the left of existing outlet

First you need to figure out the parts you need. Turn the power to the circuit off and remove the outlet. You need to figure out the gauge of the existing wiring. Since it is a 30 amp circuit, the wire should be 10 gauge, so my answer will mostly assume that.

Now you can go to the store and buy a 20 amp outlet, a face plate, a 20 amp breaker, and a breaker blank cover. Make sure you buy a breaker that is compatible with your panel. Check the outlet to make sure it can handle the wire gauge you have. If you can't find a suitable outlet that can handle 10 gauge wire, then you'll need a couple small pieces of 12 gauge wire, or a short piece of nonmetallic sheathed cable that you've stripped, and some wire nuts.

Back home: Turn off your main breaker and remove the cover from your breaker panel. Disconnect the wires going in to the existing breaker and remove the breaker. Install the new breaker and connect the black wire to the breaker. Find the bus bar where all of the white wires are connected and connect the red wire there. Put the cover back on and use the breaker blank to cover the empty spot you created from removing the double breaker.

Back at the outlet: If your outlet can't take a 10 gauge wire, use the 12 gauge wire to create pigtails: cut a black wire to about 8 inches, strip about 1 1/4 inches of insulation off each end, and use a wire nut to attach it to the 10 gauge black wire. Repeat with white (attach to red) and ground. Connect the black wire to the HOT terminal on the outlet, the white/red wire to the NEUTRAL, and the ground to the ground screw. Then push it all in to the box and put the cover on.

What I like to do is to buy a power-strip in the foreign country, then cut of its cord and replace it with a sturdy US-purchased plug. That way you don't have to modify your house or your appliances, but also don't have to use those cheap travel adapters.

If you do still want to modify your house it probably will not be as easy as when you upgrade an outlet to have USB ports because the junction box is not the same size and doesn't have the right screw holes (at least the ones that I saw in Thailand and Myanmar were not the same, although there seemed to be a wide variety so maybe you could find one), but there are electrical outlets designed for exactly what you are trying to do and sold in the USA! They are often installed in places like airports, and sometimes have the words "120v 60Hz" printed right on them. One example is the Leviton 5825-W, which can't accept as many varieties as you mentioned, but at airports in the US I've seen outlets that accept Australian and even UK plugs. I don't know the make or model number of those, but I guarantee the people building the US airports didn't buy them at a hardware store in Thailand :), so figuring out what brand those are would be better both because they match the junction box size and because they will comply with the US wiring codes (important both if you ever sell your house and if there is ever a fire at your house and the police or insurance company are investigating the cause).

(I realize that I'm responding to a question that is years old, but this page still comes up high on Google results, so hopefully this will be helpful to someone!)