看具体treaty内容，中美协议没有禁止这种情况下scholar免税，而比如泰美协议是禁止的

泰国美国免税协议里面：

Article 22最后一段：
4. The benefits provided under Article 23 (Teachers) and paragraph 1 of this Article shall, when
taken together, extend only for such period of time, not to exceed 5 taxable years from the date of
arrival of the individual claiming such benefits, as may reasonably or customarily be required to
effectuate the purpose of the visit. The benefits provided under Article 23 (Teachers) shall not be
available to an individual if, during the immediately preceding period, such individual enjoyed the benefits
of paragraph 1 of this Article.

Article 23就是免scholar 两年税的协议。所以它是明确规定如果曾经用了22(1)就不能再用23的。而中美协议没有任何地方明确禁止这种可能，这种情况是否应该是默认允许呢？请法律高手帮忙分析。

中美协议19, 20 Article:

ARTICLE 19
(Teachers, Professors and Researchers)
An individual who is, or immediately before visiting a Contracting State was, a resident of the other Contracting
State and is temporarily present in the first-mentioned Contracting State for the primary purpose of teaching, giving
lectures or conducting research at a university, college, school or other accredited educational institution or scientific
research institution in the first mentioned Contracting State shall be exempt from tax in the first mentioned
Contracting State for a period not exceeding three years in the aggregate in respect of remuneration for such
teaching, lectures or research.

ARTICLE 20
(Students and Trainees)
A student, business apprentice or trainee who is, or was immediately before visiting a Contracting State, a
resident of the other Contracting State and who is present in the first- mentioned Contracting State solely for the
purpose of his education, training or obtaining special technical experience shall be exempt from tax in that
Contracting State with respect to:
(a) payments received from abroad for the purpose of his maintenance, education, study, research
or training;
(b) grants or awards from a government, scientific, educational or other tax-exempt organization;
and
(c) income from personal services performed in that Contracting State in an amount not in excess
of 5,000 United States dollars or its equivalent in Chinese yuan for any taxable year.
The benefits provided under this Article shall extend only for such period of time as is reasonably
necessary to complete the education or training.