After the session adjourned, Thompson returned to Albany and resumed his private law practice.

[1][2][9] Thompson was reappointed as chief clerk for the legislature's regular 1907 session, which lasted from mid-January through February 23.

Over the next few years, he built a successful private law practice, bought ranch property in south central Oregon, and joined several civic and fraternal groups.

As the leader of the conservative Republican bloc in the House (a group Oregon newspapers called the Old Guard), Thompson made a very strong run for the speaker position.

When Rusk, a progressive Republican, failed to appoint conservatives to key committees, a number of Thompson supporters tried unsuccessfully to remove the speaker.

Later that year, he joined Doctor Bernard Daly and other prominent civic leaders to successfully advocate for the completion of the Nevada–California–Oregon Railway line north to Lakeview.

[25] Since Oregon state senators serve a four-year term, Thompson did not have to run for re-election prior to the opening of the 1915 legislative session.

[29][30] During the 1915 legislative session, Thompson proposed a major revision of Oregon's judicial system.

As a result, just three days after the 1915 legislative session adjourned, Withycombe appointed Daly to Lake County's new district judge position.

[39] However, Thompson lost his senate seat in the general election to Judge George T. Baldwin of Klamath Falls by one vote.

[40][41] At the time, newspapers speculated that he may have lost his seat as a result of his litigation work dealing with disputed water rights in south central Oregon.

This included a very important case, Bunting v. Oregon, that eventually was heard by the United States Supreme Court.

In that case, Thompson's client was Frank Bunting, a sawmill employee, who was challenging Oregon's ten-hour workday law.

[43][44] Another important case dealt with water rights in the Summer Lake valley and along the Chewaucan River near Paisley, Oregon.

The cattle company appealed in state court, and the district judge, Bernard Daly, reversed the water board's decision.

The developers then asked the legislature to overrule the district court, but Thompson successfully lobbied his former colleagues to prevent their intervention.

[45][46] In April 1917, Thompson decided to leave Lakeview to join a private law firm in Portland.

[2][49] Over the years in Portland, Thompson handled many high-profile cases, becoming one of Oregon's most prominent trial attorneys.

[2] In 1930, the Oregon Supreme Court appointed Thompson to prosecute George W. Joseph in a disbarment case.

[59][60][61][62] Thompson suffered a heart attack while returning from a trial in Boise, Idaho, and died at St. Charles Hospital in Bend, Oregon, on August 5, 1940.