In October 1916, Raymond Thomas, a teacher at Elko High School, was the leader of a group of hikers heading into [now-named] Thomas Canyon. When an early snowstorm hit them, Thomas stayed out there, helping the members of his group until help could arrive. By the time it did, he had perished. Today, a peak, canyon, and campground are named for Thomas. On the USGS Ruby Dome quad, the peak is simply labeled "Thomas," but locals and some others know it as Thomas Peak. A page in the summit register has a brief explanatory note about Thomas. Something to note: the peak has two summits (really three-- more info in the climbing section). The northern one is the one with the elevation on the map, but the southern one is slightly higher. However, the northern summit, being a little smaller and more precipitous, may be the more interesting one. Both are so close to one another, and there's so little elevation change between them, that there's no reason not to do both. The second-highest officially named peak in the Rubies, Thomas is also one of the quickest and easiest to climb, for the shortest way up is merely Class 2 and about 3-3.5 miles, 2 of them on a trail.
From Elko, turn onto SR 227 and drive about 20 miles to the turnoff for Lamoille Canyon. If you drive into the little town of Lamoille, you have gone about a mile too far. There is good signage in town and along the way. The road through Lamoille Canyon is paved and winds and climbs for 12 miles to Roads End, at 8800'. This is the trailhead for the northern end of the Ruby Crest National Scenic Trail.
My guess is that this is the way most people climb the peak if it is their sole objective or if it is the first part of a multi-peak outing. At the north end of the parking lot, locate the trail to Island Lake, aptly named since there is a small island in its center. Hike two miles, gaining about 800', to the lake. The cliffy peak to the northwest is Thomas Peak, the peak to the southwest is Full House Peak. Were you to head west to the saddle between Thomas and Full House, you would probably find a way, but an easier way lies north of the lake. Look for a scree slope and spot where it narrows into a gully. Clamber up the scree and then the gully and top out near the eastern end of the east ridge of Thomas. Then hike west to the southern, and higher, summit of Thomas Peak.
This route is only about 3.5 miles and gains about 2600', and it is Class 2.
This is the way I climbed the peak. It includes three distinct summits-- Liberty Peak, Full House Peak, and Thomas Peak. The daring can add Snow Lake Peak. And for those with the time, energy, and cooperative weather, there is the chance to climb Mount Fitzgerald as well. I will describe the loop in order from Liberty to Thomas since that is the way I went, but the route can be done in the opposite direction just as easily.
The way I went was via a traverse from Liberty Peak, bypassing Snow Lake Peak on the east side (it is supposed to be exposed, loose, and verging on Class 5, and I was unfamiliar with the route and already had been out longer than I told my wife I'd be) and then going over Full House, on to Thomas Peak, and then down to Island Lake. Hike south from the parking area for three miles to Liberty Pass and then head northwest to Liberty Peak (Class 2). From Liberty to the saddle between it and Snow Lake Peak, there is some Class 3, and then you go over Point 10,655 before beginning the bypass of Snow Lake Peak. Expect some more Class 3 here and there as you work from the Liberty-Snow Lake saddle to the Snow Lake-Full House saddle.
Once you are at the saddle, the best part of the route, sadly too short, is before you. It is the narrow, rotten-looking piece of ridge to the north. Expect some exposure, loose rock, and some Class 3/4 terrain. Once past that section, you have an easy walk to the top.
The route from Full House Peak to Thomas Peak is also interesting. After an easy descent to a saddle, you face a menacing-looking ridge full of cliffs and gendarmes. Instead of trying to find a way up that, stay to the east and head up a ramp. When the terrain on your west side gets a little friendlier, you can hike northeast to a broad ridge east of Thomas or opt for a more direct scrambling approach by working up and north. That second way is fun Class 3 (harder if you want it-- I found a nice little Class 4 chimney that had a small overhang to deal with as well) and takes you to some interesting subsidiary summits before getting you to the true summit of Thomas. Those subsidiary summits are smaller and more challenging to climb than the main summit, so they are definitely worth the visit. The northern summit is just a short walk north.
Follow the ridge east from Thomas Peak for nearly a mile until you can get into a rocky gully and then descend boulders and scree to gentler terrain and then to Island Lake, from which a trail leads for two miles back to the TH. In all, the traverse route as described above is about 12 miles with around 3300' of elevation gain, with Class 3 and possibly Class 4 terrain.
No red tape aside from reading and abiding by wilderness regulations posted at the trailhead.
Without needing a permit, you can camp off the trails out here. There are several campsites around Island Lake; please use one of them instead of establishing a new one. If you're doing a day climb, consider camping at Thomas Canyon Campground, which is about 3 miles down the road from Roads End. You can make summer camping reservations at recreation.gov.